In regard to a conventional solid-state imaging element, it is important to reduce the dark current on a surface of a semiconductor substrate, which causes the deterioration in image quality, and to improve the characteristic of the flicker noise or random telegraph noise of a pixel transistor in a CCD or CMOS image sensor.
One cause of the dark current is the increase of the interface state of the semiconductor substrate due to the plasma damage from UV irradiation or charge-up in the plasma treatment (CVD or dry etching) in the process of manufacturing the solid-state imaging element.
For improving the pixel characteristic of the image sensor by reducing the dark current, atoms of hydrogen or fluorine have been used to terminate the dangling bonds at the device interface.
For example, there is a technique in which the dark current on a surface of a photodiode, which is a light reception element of a semiconductor substrate, is reduced by separating hydrogen from a passivation film (SiN film) and coupling the hydrogen with a dangling bond on the surface.
In the conventional structure, however, hydrogen is supplied to the entire semiconductor substrate including a pixel portion and a peripheral circuit portion; therefore, if the amount of supplying hydrogen to the pixel portion is secured, the amount of supplying hydrogen to the fine transistor in the peripheral circuit portion becomes excessive, in which case a problem occurs in that hydrogen is in excess on the semiconductor substrate surface side to deteriorate NBTI (Negative Bias Temperature Instability).
In view of the above, a technique has been suggested in which the passivation film that supplies hydrogen is set to contain a different amount of hydrogen in the pixel portion and in the peripheral circuit portion so that the amount of hydrogen supplied from the passivation film to the semiconductor surface portion is separately controlled in the pixel portion and in the peripheral circuit portion by the sinter process (for example, see Patent Document 1).
Moreover, in recent years, various types of solid-state imaging devices have been suggested in which: one device is configured by electrically connecting a semiconductor chip whose pixel region is formed by arranging a plurality of pixels and a semiconductor chip including a logic circuit for signal processing. For example, a semiconductor module in which a rear surface irradiation type image sensor chip and a signal processing chip provided with a signal processing circuit are connected to each other with a micro-bump has been suggested.
In other words, a number of image sensors formed by stacking semiconductor chips (semiconductor substrates) have been developed.
In regard to the image sensor formed by stacking the semiconductor chips in this manner, a manufacturing method for a semiconductor device has been suggested in which: a first semiconductor wafer and a second semiconductor wafer, which are semi-finished products and respectively include a pixel array and a logic circuit, are bonded to each other; the first semiconductor wafer is thinned; the electric connection is made between the pixel array and the logic circuit; and then the product is finished as a chip and provided as a rear surface irradiation type solid-state imaging device (see, for example, Patent Document 2).